This invention relates to abrading tools, and more specifically to a self-cooling non-loading abrasive tool.
It is commonplace in industrial applications to grind a surface, whether it be ferrous or non-ferrous to achieve a desired finish. Conventional grinding operations are accomplished by the rapid rotation or reciprocation of abrading tools of various configurations, such as wheels, discs, strips, and the like. The rapid movement of the abrading tool against the work piece generates significant heat which can be a problem. Such problems include the deterioration of the grinding tool, the loss of the tool's ability to maintain desired tolerances and the rapid loading (clogging) of the abrasive particles to the extent that they no longer accurately or satisfactorily perform their function.
There have been various attempts in the prior art to improve the effects of heat generation during the abrading operation. Some such approaches simply supply air or a coolant fluid (water) directly to an abrasive tool. Other attempts utilize materials in the binder which have high heat conductivity to conduct the heat away from the surface of the tool and to remote points where coolant is provided or where air openings are provided. Such examples are illustrated and described in U.S. Pat. Nos. 3,641,718 and 3,742,655. Other materials which the prior art discloses as being useful for forming the binder matrix include rubber, polyvinyl acetate, phenol formaldehyde, rosin, urea formaldehyde, heat resistant silicon resins, and phenolic resin (U.S. Pat. No. RE 25076). While such approaches have, in general, been somewhat successful, they are for the most part expensive and do not substantially solve the loading (clogging) problem. Further such approaches are not compatible with field usage, and often result in relatively inaccurate results.
The present invention is an attempt to solve the problem by the selection of a binder material which has the characteristics of being self-cooling, as well as being resistant to loading or clogging. Such binder material has been found to exist in polytetrafluoroethylene and other similar "stick resistant" resins such as polymonochlorotrifluorethylene. Polytetrafluoroethylene (known as Teflon.TM. and Silver Stone.TM., both trademarks of DuPont) has been utilized in such products as cookware, bearings, rollers, gaskets, tubing, and electrical insultation. However, to date, it is not believed that polytetrafluoroethylene has been utilized as the binder matrix in which the abrading particles are embedded to form abrasive tools. Polytetrafluoroethylene has a unique combination of characteristics particularly adaptable for forming the binder matrix. Such characteristics include a very high melting temperature (614.degree. F.) and an extremely stubborn resistance to sticking or adhering to other materials.
Therefore, in general the present invention is directed to a self-cooling, non-loading abrading tool for sanding, grinding, or polishing work pieces which tool is formed by embedding the multiplicity of abrasive particles (such as 4% silica sand) in a binder matrix formed primarily of virgin polytetrafluoroethylene. The binder matrix may further include a stiffening agent such as ground glass (15%-25%).
The abrading tool may be molded or formed in a variety of sizes, shapes and configurations such as wheels, discs, plain and tapered cups, sheets, pads, and the like. Abrading tools formed in compliance with the present invention may be utilized in connection with the grinding of ferrous and non-ferrous materials including such difficult materials to abrade as fiber glass and aluminum. The abrasive particles may include, in addition to silica sand, diamond, carborundum, garnet, alumimum oxide, pumice, rouge, tripoli, and the like.
Although the abrading tool according to the present invention is primarily designed to be used without any type of coolant, it can also be used with splash water or coolant if desired. The primary feature of the invention is the non-loading or non-clogging characteristic. Additionally, the heat generated by the abrading operation is minimized as the only temperature increase occurs in the abrasive particles themselves, the polytetrafluoroethylene being substantially frictionless because of the substitution of fluorine for hydrogen in the polymer.
Tests have shown that such abrading wheels or discs may be operated in excess of 5000 rpm. Other possible variations in the material of the binder matrix include polymonochlorotrifluoroethylene, however, even though it is also very resistant to sticking to other materials (and thus non-clogging), the melting point is only approximately 300.degree. F.
It is therefore an object of the present invention to provide a self-cooling, non-loading abrading tool.
It is another object of the present invention to provide a tool of the type described in which the abrasive particles are embedded in a binder matrix that is resistant to sticking.
It is yet another object of the present invention to provide a tool of the type described in which the binder matrix is formed primarily of polytetrafluoroethylene.